Effects of carbon and Ti on damping capacity are investigated in an Fe-17%Mn alloy. The suppressive force of carbon against ${gamma}{ ightarrow}{varepsilon}$ transformation increases linearly with an increase in its content, lowering Ms temperature and volume fraction of ${varepsilon}$ martensite. Carbon deteriorates damping capacity by reducing the interfacial area of damping sources and mobility of the boundaries contributing to anelastic deformation. The reduction in damping capacity is accelerated when carbon-containing alloy is aged at higher temperatures above room temperature. The effect of Ti on damping capacity is found to be benificial in carbon-containing alloy, which is attributed to the depletion of carbon solute due to the formation of TiC.